This invention relates to a pneumatic tire, and more particularly to a preshaped green tread strip for use in belted tires and an improved method of making belted tires.
The manufacturing of a bias belted or radial belted tire generally comprises building a first carcass body ply structure on a cylindrical building drum. The carcass body ply generally comprises of an inner liner, a cord reinforcing ply structure and two bead cores one at each axial end thereof. The carcass body structure is then shaped into a torodial configuration similar to the overall configuration of the final cured tire, except slightly smaller. A belt reinforcing ply structure is placed about the circumference of the carcass body. A strip of uncured tread stock is then placed circumferentially about the belt structure. The tire is then placed into a mold where it is expanded, shaped and vulcanized into its final configuration. During this molding process the tread rubber flows into the void areas of the mold thereby forming the tread pattern on the tire.
A pneumatic tire is a complex, dynamic article of manufacture in which all the components interact to achieve an overall performanace. The tire designer selects each component so as to optimize the overall performance of the tire. The tread compound has a substantial effect upon the overall performance of the tire. The particular compound that is selected by the tire designer is determined upon the basis of both its good and adverse attributes. It has been found desirable to use tread compounds which have a high degree of stiffness for high performance characteristics. However, the use of high stiffness compounds in the prior art under conventional tire building methods has caused extreme nonuniformity of the belt reinforcing structure in the cured tire. Belt nonuniformity can in turn cause vibrational and durability problems which may result in poor performance and/or premature failure of the tire.
In accordance with applicant's invention, compounds having high stiffness may be used in the conventional tire building process without the nonuniformity problems experienced in the prior art.